# Chemistry-EQUILIBRIUM

posted by
**Karen** on
.

I'm working on this equilibrium homework problem and I'll post all my work. Can you help me please? I'm a little stuck especially on the polynomial.

**If iodine vapor and bromine vapor are reacted in 15o degree C they form idodine monobromide gas. At 150 degrees C the value of Kc is known to be 125. Lets say we placed 5.73 g of I2 and 4.91 g of Br2 into a 5.00L flask and heat it to 150 degrees C.
find the value of the final equilibrium concentrations of all reactants and products of M?
**

so far this is what i have:

When converting I2 to mols I got 0.0226 mols and divided by 5.00L gives me 0.00452 M.

For Br 2 i got 0.0307 mol and divided by 5.00 L gives me 0.00614 M.

(Q=0 b/c no products exist initially)

i would prefer to use as simple math as possible, so i didn't use multiple variables.

let 2x=IBr

x=I2

x=Br2

so the expression from that is:

2x^2/(0.00452-x)(0.00614-x)=125

when expanded, for the polynomial, i calculated

4x^2/(2.76X10^-5 - 0.00452x-0.00641x - .00345)

4x^2 = 125x^2-.7675X-.565x-.00345

0 = 121x^2 - .7675x-.565x-.00345

so i solved for x using the quadratic formula and i received

-1.3325+- square root(-1.3325)^2-4(125)(.000345)/ 2(121)

-1.3325+-.3253/242

x=-.00685 and -.50365 that can't be right can it?

negative values wouldn't work for the domain correct?